1. Field of the Invention
The present invention relates to a protective sheath (conduit) against radiation, in particular from the electric field generated by electric cables extending inside the sheath, for example of the ICTA or ICTL type.
2. Description of the Related Art
So-called “shielded” cables are known which are used in order to transmit high-frequency telecommunications signals, either by means of a copper conductor, or by means of an optical fibre, etc. The shielding is generally produced using a braid made of a conductive metal wire which is separated from the conductive wire or from the optical fibre by a layer of insulating plastic material, and is surrounded on the outside by another layer of insulating plastic material.
Currently, protective sheaths called ICTA, ICTL sheaths (conduits), etc. are commonly used in the building industry, the outer surface of which is smooth or corrugated in order to give them a certain flexibility whilst reinforcing their resistance to crushing. These sheaths have no shielding against radiation, and in particular, against electric fields.
These protective sheaths receive several electric cables, generally a neutral cable, an earth cable and a phase cable connected to the electrical distribution network, the frequency of which is usually 50 Hz. They can also receive telecommunications cables used for transmitting telecommunications signals.
The cables are intended to supply power to various devices or power outlets.
These cables generate an electric field which can interfere with certain devices, or certain telecommunications signals, or even cause health problems.
In WO 2006/016048, the Applicant created and described a protective sheath against radiation, in particular from the electric field, generated by electric cables of the above type.
The sheath described in the above document comprises an outer layer made of electrically insulating material which covers an inner layer made of electrically conductive material. The end of the sheath comprises removable connection means for connecting the layer of electrically conductive material to an electrical conductor intended to be connected to earth, said sheath surrounding or being intended to surround at least a neutral cable, an earth cable and a phase cable connected to the electrical distribution network.
The electrically conductive layer connected to earth very greatly attenuates the radiation towards the outside of the electric field generated by the cables extending inside the sheath.